The present invention relates to an oxygen-absorbing resin composition and a laminate thereof.
Recently, various plastic containers have been used for the packaging because of their advantages such as light weight, transparency and easiness of molding.
Because an oxygen barrier property of the plastic containers is lower than that of metal containers and glass containers, the plastic containers have problems in that the contents of the containers are denatured and the flavor thereof is reduced.
For preventing these problems the plastic container walls have a multi-layer structure in which at least one layer is made of a resin having an excellent oxygen barrier property such as ethylene/vinyl alcohol copolymer. There are other kinds of containers having an oxygen-absorbing layer for absorbing oxygen remaining in the containers and also oxygen penetrating into the containers from the outside. Oxygen absorbers (disoxidants) used for forming the oxygen-absorbing layer include, for example, those mainly containing a reducing substance such as iron powder (see, for example, Official Gazette of Japanese Patent Kokoku No. Sho 62-1824) and those containing an oxygen scavenger composed of an ethylenically unsaturated hydrocarbon and a transition metal catalyst (Official Gazettes of Japanese Patent Kokai Nos. 2001-39475 and Hei 5-115776 and Japanese Patent Kohyo No. Hei 8-502306).
However, although a method wherein an oxygen absorber such as iron powder is incorporated into a resin to be used for forming a packaging material for a container wall is satisfactory in regard to the oxygen absorbing capacity, the use of the packaging material is limited to the field of packages, in which a high transparency is not required, because the resin is colored a specified hue. In the method wherein the oxygen scavenger composed of an ethylenically unsaturated hydrocarbon and a transition metal catalyst is used, a relatively large amount of the ethylenically unsaturated hydrocarbon must be used because the ethylenically unsaturated hydrocarbon per se absorbs oxygen to exhibit the oxygen barrier property. However, when the relative amount of the ethylenically unsaturated hydrocarbon is increased, a problem in which the moldability and transparency of the resin composition deteriorates occurs. The period of effectively absorbing oxygen is limited under these conditions. Therefore, this method cannot satisfy the requirement of storage for a long period of time. In addition, coloring and a smell are caused by the absorption of oxygen.